HAL Id: jpa-00218605
https://hal.archives-ouvertes.fr/jpa-00218605
Submitted on 1 Jan 1979
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
THE STRUCTURES OF MARTENSITE AND BAINITE
H. Ino, T. Itō
To cite this version:
H. Ino, T. Itō. THE STRUCTURES OF MARTENSITE AND BAINITE. Journal de Physique Col-
loques, 1979, 40 (C2), pp.C2-644-C2-646. �10.1051/jphyscol:19792224�. �jpa-00218605�
JOURNAL DE PHYSIQUE
Colloque C2, suppl&menl au n o
3,Tome
40,mars
1979,page C2-644
THE STRUCTURES OF MARTENSITE AND B A I N I T E
H. Ino and T. It5
I n s t i t u t e o f Industm'al Science, lhziversity o f Tokyo, Roppongi, Minato-Ku, Tokyo 106, J a p m
RLsum6.- Les spectres ~Essbauer du 5 7 ~ e dans la martensite et ses structures de recuit ont Lt6 analys6s en six contributions, classges suivant le nombre et la distance des atomes de carbone les plus proches. Sur cette base, les configurations atomiques locales et la nature des liaisons ont St6 d6crites dans FesC et le carbure E; on a confirm6 6galement la validit6 du modsle d'occu- pation des sites t6tra6driques pour la phase martensitique 2 basse temp6rature.
Les spectres Mzssbauer de la bainite montrent que la structure du carbure form6 ?2 0 0 ~ ~ i est proche du carbure E, contrairement 5 la c6mentite f o 6 e 2 250°C.
Abstract.- The %ssbauer spectra of 5 7 ~ e in martensite and its aged structures were throughout re- solved into six components, classified by the number and the distance of the nearest carbon atoms.
On this basis, we analyzed the local atomic configuration and bonding nature in FesC and E carbide, and also confirmed the validity of the tetrahedral site occupation model for the low temperature martensite phase.
The Mzssbauer spectra of lower bainite showed that the carbide structure formed at 200'~ are close to E carbide, in contrast to cementite at 250'~.
1. Sample pre~aration.- High purity (>99.99%) iron foils were carburized in a mixture of Hz and CO (or CHI,) gases at 900~950'~. To obtain fresh mar- tensite, the carburized specimen was quenched into iced water and immediately transfered to a liquid nitrogen bath. The carbon content of the specimen
(0.6s1.3 wt%C) was estimated from the tetragonality measurements by X-ray diffraction. The lower baini- te structure was obtained by quenching and austem- pering the carburized specimen in a silicon oil bath at 200~250'~.
2. The structure of martensite.- In figure
I ,
the spectrum A of as-quenched martensite was resolved into three ferromagnetic components a, b and c. By aging at 20°c, the intensity of the "b" component rapidly decreased b'ut that of the "c" increased.The internal magnetic field of the main component
11 a decreased. The results are similar to those of 1 1
previous reports /I/-161. The components denoted as "d" and "e" appeared after aging at 20°C and were intensified by aging at 80°c and 90°C. The "b"
component completely disappeared at 80'~.
Figure 2 shows the spectrum after aging at 140°c, together with that of the specimen aged at room temperature and of pure iron (solid line), normalized in absorption area. The "d" component disappeared after ageing at 140'~. The "e" and probably "c", too, remained, of which the values of internal field are very close to each other. A com- ponent "f" also appeared, which has a much smaller internal magnetic field. The intensities of central
paramagnetic peaks were unchanged, meaning that the E carbide phase formed at 140°C was not superparama- gnetic in contradiction to previous works /1/,/7/,/8/.
A
-
As quenched (low temp phose) 6 - Aged ot 201: X 3hrC
-
Aged ot 201: X 76hr 0 - Aged at 80.C X 1 hrA (measured at 77K )
,--.
, . - .
-.
I -. ..
,-d l . li
e5 ' 06 e6
I
I I I I I I II
- 6 4 - 2 0 2 4 6
Velocity (mmls)
Fig. 1 : ~Essbauer spectra for the same specimen of Fe-l.Zwt%C, as quenched and aged up to 80'~.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792224
Water quenched. aqed at r t
c
JI I I I I I
I
6 -L -2 0 2 4 6
Velocity ( m m l s )
Fig. 2
:Mijssbauer spectra for the specimen of Fe- I.Zwt%C after ageing at room temperature and 140°C (measured at 300
K).Figure
3is the spectrum of the same specimen measured at 4.2 K under an effective external
ma-gnetic field of 3.4 T(34 kOe) parallel to the direc- tion of
yrays to erase out the 2nd and 5th peaks (f1/2
++1/2 transition). The spectrum is clearly resolved into three components "a", "e" (plus "c") and "f", with the values of internal field Hi of 33.8, 27.1 and 18.6 T, respectively. A similar mea- surement for the specimen aged at 90°C for 1 hr showed that the "f" component with Hi
=19.2 T exists even at 90'~.
t
a1 Measured at 42 K. k t . = 3.4T* I
Fig. 3
:Gssbauer spectrum for the same specimen as in figure 2, measured under an applied magnetic field of 3.4T parallel to
yray direction.
In our previous paper /9/, we examined the relation between the reduction of internal magnetic field from that for pure iron Hio and the number of the 1st nearest carbon atoms n in various Fe-C alloys and compound, and derived the rule that the reduction AHi(= Hio-Hi) is nearly proportional to n and that (AHi/HiO)/n is about 0.2. The rule is based on the nature of localized characters of bonding, and thereafter has been widely applied to other
metal-metalloid systems /lo/, /11/.
From this point of view, present results can be thoroughly explained. Both the "c" and "e" compo- nents having Hi/Hi0=0.8 are related to iron atoms neighboured by one nearest octahedral carbon atom, and the "f" component with H./Hi0~0.56 is related to those surrounded by two nearest carbon atoms. The
I I
b
t tcomponent having H./HiO=0.95 can be identified as
the absorption arising from four 1st neighbouringiron atoms of the tetrahedral by co-ordinated carbon, where the distance between iron and carbon is longer than that when carbon occupies octahedral positions. The tetrahedral site occupation model for low tempera- ture martensite 12, /3/,
/12/is, therefore, consis- tent with the above consideration.
The "a" and "d" components arise from iron atoms without 1st nearest carbon atoms. Considering from the effect of the 2nd and 3rd nearest carbon atoms, the enhancement of internal field /13/ may be assumed to result in H./HiO-1.14 for "dl1.
By considering experimental evidences of the superlattice of Fe4C /I41 and of its long period structure /IS/ formed after ageing around 80°C, it is concluded that the "d" component arises from the corner iron atoms of Fe4C lattice and "f" from the face centre iron atoms surrounded by two carbon neighbours. Quadrupole coupling (E=-0.08 mm/s) of "e"
is about a half of the value fo "c" and opposite in sign. The "c" and "e" components are, therefore, identified as due to face-centred iron atoms surroun- ded by one carbon atom, spin directions of which are parallel and perpendicular, respectively, to the principal axis
qof electric field gradient.
The "e" (including "c") and "f" components exist after aging at 140°c (in Fig
31,where hexa- gonal
Ecarbide (or slightly distorted to orthorhom- bic n carbide) is formed. The local atomic configu- ration and bonding nature in this coherent precipi- tates are almost unchanged. Our spectrum analysis for
E
carbide agrees well with that by Foct et al. 1161, but inconsistent with those by others /8, 17/.
3. The structure of bainite.- The Gssbauer effect and X-ray diffraction measurements showed that car- bide formed in bainite at 250'~ is surely cementite (Fe3C) from early stage of tempering. While, in con- trast, the Gssbauer spectrum observed for the spe- cimen austempered at
200°Cwas similar to but sligh- tly different from that of
Ecarbide.
No one have examined by diffraction the carbide
structure in bainite formed at such a low temperatu-
re, probably because of its small size beyond obser-
vation. In the present experiments, it is clarified
c2-646 JOURNAL DE PHYSIQUE
t h a t e v e n i n t h e c a s e o f Fe-C b i n a r y s y s t e m w i t h o u t S i , c a r b i d e formed a t low t e m p e r a t u r e i s c l o s e t o E c a r b i d e i n i t s l o c a l a t o m i c c o n f i g u r a t i o n .
R e f e r e n c e s
/ I / Genin, J . R . a n d F l i n n , P.A, T r a n s . Met. Soc. AIME 242 (1968) 1419.
-
/ 2 / F u j u t a , F.E., M o r i t a , T. a n d I n o , H . , T r a n s . I r o n S t e e l I n s t . J a p a n ,
11,
S u p p l . P r o c . ICSTIS (1971) 1273./ 3 / L e s o i l l e , M. a n d G i e l e n , P.M., Met. T r a n s .
2
(1972) 2681./ 4 / Choo, W.K. a n d Kaplow, R., A c t a Met.
2
(1973) 725./ 5 / F u j i t a , E.E., S h i g a , C., M o r i t a , T. and I n o , H.,
Nippon Kinzoku-gakkai s h i x (1974) 1030 ( i n J a p a n e s e ) . 1 6 1 G r i d n e v , V . N . , G a v r i l y k , V . G . , Nemoshikalenko, V.V.,
P o l y s h k i n , Y.A. and Razymov, O.N., F i z . M e t a l . Metal- l o v e d .
42
(1977) 582.1 7 1 Ron, M., S c h e c h t e r , H. a n d Niedzwiedz, S. J. Appl.
Phys. x ( 1 9 6 8 ) . 265.
1 8 1 L e C a e r , G., Simon, A . , L o r e n z o , A. and Genin, J . M . Phys. S t a t u s S o l i d i ( a )
5
(1971) K97./ 9 / I n o , H . , M o r i t a , T . , F u j i t a , F.E., Maeda, Y . , Ono, Y . a n d I n o k u t i , Y . , J . Phys. Soc. J a p a n
5
(1968) 8 8 . / l o / F a t s e a s , G.A., Phys. S t a t u s S o l i d i ( b )2
(1973) K23./ ] I / M o r i t a , T . , Swnitomo, Y . , I n o , H . , F u j i t a , F.E. a n d Maeda, Y . , J . Phys. Soc. J a p a n
35
(1973) 1378./ I 2 1 Lysak, L . I . a n d Vovk, Ya.N., Phys. M e t a l . M e t a l l o g . 2 (1965) 52;
20
( 1965) 63.1131 Moriya, T . , I n o , H . , F u j i t a , F.E. and Maeda, Y . , J . P h y s . Soc. J a p a n
24
( 1968) 60./ 1 4 / I s o t o v , V . I . a n d U t e v s k i y , L.M., F i z . MEtal. M e t a l l o v e d . 25 (1968) 98.
-
/IS/ Nagakura, S . , S h i r a i s h i , K. and Toyoshima, M . , T r a n s . J a p a n I n s t . M e t a l s
11,
S u p p l . P r o c . 1 s t JIM I n t . Sym.(1976) 299.
/ 1 6 / F o c t , J . , Dubois, J . M . and Le C a e r , G . , J . P h y s i q u e C o l l o q .
35
(1974) C6-493.1 1 7 1 A r e n t s , R.A., Maksimov, Yu-Y., S u z d a l e c . I.P. I m s h e n n i k , V.K. and Krupyansky, Yu.F., F i z . M e t a l . M e t a l l o v e d .
36
(1973) 277.
